Roughly chop the onion, cubanelle, bell pepper, ajicitos, and tomatoes. They do not need to be pretty. They are going in the food processor.
Add all the chopped vegetables to a food processor along with the peeled garlic cloves, cilantro, and culantro.
Add the olive oil, vinegar or naranja agria juice, oregano, salt, and annatto if using.
Pulse 8 to 10 times, scraping down the sides between pulses, until you reach the texture you want. Some Dominican cooks like a chunky sofrito with visible bits of pepper. Others prefer a smooth puree. There is no wrong answer.
Taste and adjust. If it is missing brightness, add more vinegar or lime. If it is missing depth, add another garlic clove. If it is missing heat, add half an ajicito picante (Scotch bonnet) and pulse once more.
Transfer to a clean glass jar for the refrigerator or to ice cube trays for the freezer.